What type of fasteners and connectors are used for sheet metal ductwork in the GTA?

Sheet metal ductwork in GTA residential installations uses a combination of self-drilling screws, rivets, cleats, draw bands, and slip connectors to create secure, airtight joints that hold up under decades of thermal cycling and system vibration. The specific fasteners and connectors vary depending on whether the ductwork is round or rectangular, and each serves a distinct purpose in the overall assembly.

Self-drilling sheet metal screws (commonly called TEK screws or zip screws) are the most widely used fastener in GTA residential ductwork. These are typically #8 or #10 hex-head screws with a drill-point tip that cuts through galvanized steel without a pilot hole. They are driven with a magnetic hex-head driver on a cordless drill and take seconds to install. Most GTA contractors use three to four screws at each round duct joint (evenly spaced around the circumference) and screws every 4 to 6 inches along rectangular duct seams and cleat connections. These screws cost just pennies each but are the primary mechanical fastening holding the entire system together.

Rivets — specifically POP rivets (blind rivets) — are used in situations where screw heads protruding into the duct interior would cause turbulence or noise, or where a cleaner exterior appearance is desired. This is especially common on exposed spiral duct installations in basement renovations across Toronto, where the aesthetic of the ductwork matters. Rivets are installed with a hand rivet gun and create a flush, permanent connection. They cost slightly more in labour time than screws but produce a much cleaner finish.

S-cleats and drive cleats are the connectors used to join rectangular duct sections. An S-cleat is a folded strip of galvanized steel that hooks over the edges of two mating duct sections, locking them together. Drive cleats are flat channels hammered onto the remaining two sides to complete the four-sided connection. Together, they form a rigid mechanical joint that holds the rectangular profile together. These are fabricated by the sheet metal shop or purchased as standard fittings from HVAC supply houses across the GTA. A typical residential installation uses dozens of cleats — they cost $2 to $5 each.

Draw bands and clamps are used with round duct connections, particularly on larger diameter trunk lines and where spiral duct meets fittings. A draw band is a metal strap that wraps around the outside of a joint and is tightened with a bolt, compressing a gasket or simply clamping the overlapping sections together. These are standard on spiral duct beaded slip connections and provide a strong, adjustable connection.

Hanger straps and supports are the often-overlooked connectors that keep the entire system in place. Galvanized hanger strap (typically 1-inch wide perforated metal strapping) supports horizontal duct runs from floor joists, with supports required every 4 to 5 feet for round duct and every 4 feet for rectangular duct. Proper support prevents sagging, which creates low points where condensation collects and joints separate over time — a common problem in older GTA homes where original hangers have corroded or loosened.

After all mechanical fastening is complete, every joint must be sealed with duct mastic or UL 181 foil tape. The fasteners hold the ductwork together structurally; the sealant makes it airtight. Both are essential — fasteners without sealant create a leaky system, and sealant without fasteners will eventually separate under thermal stress and vibration. Quality GTA ductwork contractors use both without exception.